A. Field of the Invention
The present invention is directed to improved methods for treating cotton-containing fabrics and non-cotton containing cellulose fabrics with cellulase as well as to the fabrics produced from these methods. In particular, the improved methods of the present invention are directed to contacting cotton-containing fabrics and non-cotton containing fabrics with an aqueous solution containing a cellulase composition which comprises one or more truncated cellulase enzymes.
B. State of the Art
During or shortly after their manufacture, cotton-containing fabrics can be treated with cellulase in order to impart desirable properties to the fabric. For example, in the textile industry, cellulase has been used to improve the feel and/or appearance of cotton-containing fabrics, to remove surface fibers from cotton-containing knits, for imparting a stone washed appearance to cotton-containing denims and the like.
In particular, Japanese Patent Application Nos. 58-36217 and 58-54032 as well as Ohishi et al., "Reformation of Cotton Fabric by Cellulase" and JTN December 1988 journal article "What's New--Weight Loss Treatment to Soften the Touch of Cotton Fabric" each disclose that treatment of cotton-containing fabrics with cellulase results in an improved feel for the fabric. It is generally believed that this cellulase treatment removes cotton fuzzing and/or surface fibers which reduces the weight of the fabric. The combination of these effects imparts improved feel to the fabric.
Additionally, it was heretofore known in the art to treat cotton-containing knitted fabrics with a cellulase solution under agitation and cascading conditions, for example, by use of a jet, for the purpose of removing broken fibers and threads common to these knitted fabrics.
Clothing made from cellulose fabric, such as cotton denim, is stiff in texture due to the presence of sizing compositions used to ease manufacturing, handling and assembling of clothing items and typically has a fresh dark dyed appearance. One desirable characteristic of indigo-dyed denim cloth is the alteration of dyed threads with white threads, which gives denim a white on blue appearance.
After a period of extended wear and laundering, the clothing items, particularly denim, can develop in the clothing panels and on seams, localized areas of variation in the form of a lightening, in the depth or density of color. In addition, a general fading of the clothes, some pucker in seams and some wrinkling in the fabric panels can often appear. Additionally, after laundering, sizing is substantially removed from the fabric resulting in a softer feel. In recent years such a distressed or "stonewashed" look, particularly in denim clothing, has become very desirable to a substantial proportion of the public.
Previous methods for producing the distressed look included stonewashing of a clothing item or items in a large tub with pumice stones having a particle size of about 1 to 10 inches and with smaller pumice particles generated by the abrasive nature of the process. Typically the clothing item is tumbled with the pumice while wet for a sufficient period such that the pumice abrades the fabric to produce in the fabric panels, localized abraded areas of lighter color and similar lightened areas in the seams. Additionally the pumice softens the fabric and produces a fuzzy surface similar to that produced by the extended wear and laundering of the fabric. This method produced the desired white on blue contrast described above.
The use of the pumice stones has several disadvantages, including overload damage to the machine motors, mechanical damage to transport mechanisms and washing drums, environmental waste problems from the grit produced and high labor costs associated with the manual removal of the stones from the pockets of the garments.
In view of the problems associated with pumice stones in stonewashing, cellulase solutions are used as a replacement for the pumice stones under agitating and cascading conditions, i.e., in a rotary drum washing machine, to impart a "stonewashed" appearance to the denim (U.S. Pat. No. 4,832,864).
Cellulases are enzymes which hydrolyze cellulose (.beta.-1,4-D-glucan linkages) and produce as primary products glucose, cellobiose, cellooligosaccharides, and the like. Cellulases are produced by a number of microorganisms and comprise several different enzyme classifications including those identified as exo-cellobiohydrolases (CBH), endoglucanases (EG) and .beta.-glucosidases (BG) (Schulein, M, 1988 Methods in Enzymology 160:235-242).
The enzymes within these classifications can be separated into individual components. For example, the cellulase produced by the filamentous fungus, Trichoderma longibrachiatum, hereafter T.longibrachiatum, consists of at least two CBH components, i.e., CBHI and CBHII, and at least four EG components, i.e., EGI, EGII, EGIII and EGV (Saloheimo, A. et al 1993 in Proceedings of the second TRICEL symposium on Trichoderma reesei Cellulases and Other Hydrolases, Espoo, Finland, ed by P. Suominen & T. Reinikainen. Foundation for Biotechnical and Industrial Fermentation Research 8:139-146) components, and at least one .beta.-glucosidase. The genes encoding these components are namely cbh1, cbh2, egl1, egl2, egl3, and egl5 respectively.
The complete cellulase system comprising CBH, EG and BG components synergistically act to convert crystalline cellulose to glucose. The two exo-cellobiohyrolases and the four presently known endoglucanases act together to hydrolyze cellulose to small cello-oligosaccharides. The oligosaccharides (mainly cellobioses) are subsequently hydrolyzed to glucose by a major .beta.-glucosidase (with possible additional hydrolysis from minor .beta.-glucosidase components).
A problem with the use of complete cellulase compositions from Trichoderma sp. microorganisms and other fungal sources for stonewashing dyed denim is the incomplete removal of colorant caused by redeposition or backstaining of some of the dye back onto the cloth during the stonewashing process. In the case of denim fabric, this causes recoloration of the blue threads and blue coloration of the white threads, resulting in less contrast between the blue and white threads and abrasion points (i.e., a blue on blue look rather than the preferred white on blue). See, American Dyestuff Reporter, September 1990, pp. 24-28. This redeposition is objectionable to some users.
Trichoderma cellulases, even though they result in backstaining are preferred because of their higher activity on denim material. In addition, cellulases with a higher degree of purity may be beneficial in the present invention. High specific activity or a high level of purity results in a higher degree of abrasion in a significantly shorter processing time and therefor, is preferable to the denim processors.
Attempts to reduce the amount of redeposition of dye included the addition of extra chemicals or enzymes, such as surfactants, proteases or other agents, into the cellulase wash to help disperse the loosened dye. In addition, processors have used less active whole cellulase, along with extra washings. However, this results in additional chemical costs and longer processing times. Another method includes the use of a mild bleach agent or stain removing agent in the process. This method affects the garment's final shade and increases the processing time. Finally the use of enzymes and stones together leave the processor with all the problems caused by the use of the stones alone. Accordingly, it would be desirable to find a method to prevent redeposition of colorant during stonewashing with cellulases.
Protein analysis of the cellobiohydrolases (CBHI and CBHII) and major endoglucanases (EGI and EGII) of T. longibrachiatum has shown that a bifunctional organization exists in the form of a catalytic core domain and a smaller cellulose binding domain separated by a linker or flexible hinge stretch of amino acids rich in proline and hydroxyamino acids. Genes for the two cellobiohydrolases, CBHI and CBHII (Shoemaker, S et al 1983 Bio/Technology 1, 691-696, Teeri, T et al 1983, Bio/Technology 1, 696-699 and Teeri, T. et al, 1987, Gene 51, 43-52) and two major endoglucansases, EGI and EGII (Penttila, M. et al 1986, Gene 45, 253-263, Van Arsdell, J.N/ et al 1987 Bio/Technology 5, 60-64 and Saloheimo, M. et al 1988, Gene 63, 11-21) has been isolated from T. longibrachiatum and the protein domain structure has been confirmed.
A similar bifunctional organization of cellulase enzymes is found in bacterial cellulases. The cellulose binding domain (CBD) and catalytic core of Cellulomonas fimi endoglucanase A (C. fimi Cen A) has been studied extensively (Ong E. et al 1989, Trends Biotechnol. 7:239-243, Pilz et al 1990, Biochem J. 271:277-280 and Warren et al 1987, Proteins 1:335-341). Gene fragments encoding the CBD and the CBD with the linker have been cloned, expressed in E. coli and shown to possess novel activities on cellulose fibers (Gilkes, N. R. et al 1991, Microbiol. Rev. 55:305-315 and Din, N et al 1991, Bio/Technology 9:1096-1099). For example, isolated CBD from C. fimi Cen A genetically expressed in E. coli disrupts the structure of cellulose fibers and releases small particles but has no detectable hydrolytic activity. CBD further possess a wide application in protein purification and enzyme immobilization. On the other hand, the catalytic domain of C. fimi Cen A isolated from protease cleaved cellulase does not disrupt the fibril structure of cellulose and instead smooths the surface of the fiber.
Trichoderma longibrachiatum CBHI core domains have been separated proteolytically and purified but only milligram quantities are isolated by this biochemical procedure (Offord D., et al 1991, Applied Biochem. and Biotech. 28/29:377-386). Similar studies were done in an analysis of the core and binding domains of CBHI, CBHII, EGI and EGII isolated from T. longibrachiatum after biochemical proteolysis, however, only enough protein was recovered for structural and functional analysis (Tomme, P et al, 1988, Eur.J. Biochem 170:575-581 and Ajo, S, 1991 FEBS 291:45-49). Accordingly, the prior art has failed to recognize the improvements possible in textile processing when using cellulase core domain or cellulose binding domain regions.